"She did have injuries to her arms, to her legs, to her back, to certain other lower areas that we believe are the result of the type of abuse that I've described," said Chris Trim of the Elk Grove Police Department.

Elk Grove police say the boy, who has responsibility for the care of his 51-year-old mother, is in juvenile hall.

The boy was interviewed at Foulks Ranch Elementary School on Monday, and he was later arrested at his home.

Sacramento County prosecutors charged him with assault with a deadly weapon and elder abuse.

In a juvenile court hearing on Thursday, judge Natalie Lindsey continued the case until next Monday. The boy is likely to remain in custody until that time.

Trim says the mother suffers from a medical condition that requires a caregiver to prepare meals and do laundry.

It is unclear how the boy became the primary caretaker.

Neighbors told KCRA 3 no one from the family talked about it -- not even to friends like Dinah Whited, whose granddaughter frequently played with the boy.

"Nobody knew what was going on," Whited told KCRA 3.

"Because I know he didn't tell us, because he spend a lot of time at my house. They study together, we take him camping. If I had known that was going on I would have checked on her," Whited said.

KCRA 3 tried talking to the boy's father outside of court today, but he declined to answer any questions and drove off without saying a word.